Wander to the back of the queue with a growl (3)
I believe the answer is:
err
'wander' is the definition.
(to err is to go astray)
'the back of the queue with a growl' is the wordplay.
'the back of the' says to take the final letters.
'with' is a charade indicator (letters next to each other).
'a growl' becomes 'rr' (I can't explain this - if you can you should give a lot more credence to this answer).
The final letter of 'queue' is 'e'.
'e'+'rr'='ERR'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for err that I've seen before include "Drop a clanger" , "Be inaccurate" , "Make mistakes" , "Transgress" , "Boob" .)